Amplifier based on a field-effect triode with negative current feedback

Conclusions A field-effect triode amplifier with series negative current feedback allows a voltage gain of the order of 200–300 to be obtained for a load resistance R_s1 M. The coefficient K_u begins to decrease noticeably only for a feedback resistance above 500 .The current gain reaches (8–10)·10³. Increasing the resistances R_s and R_L to hundreds of ohms has practically no effect on K_i. For a further increase of R_s and R_L the coefficient K_i decreases.The power gain reaches its maximum value (of the order of 10⁴ or more) for R_s100 and R_L=10–100 k. An increase in R_s leads to a reduction of K_pmax and to a shift of the extremum of the function K_p=f(R_L) into the range of higher values of R_L.A large input resistance of the amplifier (tens of megohms and higher) is obtained when R_s increases to 10–100 M. The maximum input resistance is obtained for R_L and R_s and may exceed values of from hundreds of megohms to several gigaohms. The minimum input resistance is hundreds of kilohms for R_L and R_s0.The minimum input resistance (5–10 k or less) is ensured for R_g and R_L0. An increase of the output resistance to hundreds of megohms or higher occurs for R_g and R_s.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 67–70, September, 1971.     

Study of thermal and gasdynamic characteristics of a subsonic plasma air jet

Results are presented from a numerical analysis and experimental study of the enthalpy and velocity distributions along and across a subsonic plasma air jet.Notation x, r axial and radial coordinates - u, v axial and radial components of velocity - density - viscosity - emissivity - r_0.5 radius at which local value of velocity or enthalpy is half its axial value - , radii of dynamic and thermal boundary layers - q heat flux, kW/m² - h, h_w stagnation enthalpy and enthalpy at wall temperature, kJ/kg - p, p stagnation pressure and static pressure, Pa - R radius of curvature of spherical front part of body Indices 0 teconditions at nozzle edge - m conditions on jet axis - conditions on outer boundary of jet Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 34–39, January, 1982.     

Structure of flows in vortices

The structure of a gradient vortical flow was studied experimentally.Notation v_x, v_y, v_z flow velocity components in a rectangular coordinate system - v, v_r, v_z flow velocity components in a cylindrical coordinate system - v₁ tangential velocity at the boundary of solid revolution at r = r₁ - l length of the vortex - kinematic viscosity - R radius of the forming cylinder - circulation in the region of potential flow - second air flow rate through the eddy of ascending flows - Re=v₁r₁/ tangential Reynolds number - N=Q/r_o radial Reynolds number - a=l/r₀ configuration ratio for the vortex model - s=r_o/2Q effective exchange coefficient - a ^*=l/r configuration ratio for the vortex generator - s^*=R/Q constructive exchange coefficient - p=p–p pressure drop in the vortex relative to atmospheric pressure p - r^*= r/r₁ dimensionless radius of the vortex - v^*=v/v₁ dimensionless tangential velocity - a ^*/a gradient ratio Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 4, pp. 611–618, October, 1980.     

Further properties of the Falkner-Skan equation

Summary We present some analytical perturbation results from which the skin-friction is accurately predicted over the range 1/2<<, where is the usual Falkner-Skan parameter. The first eigenvalue for various in the range 2<< is also calculated numerically and certain properties noted. We find, analytically, the whole set of eignesolutions for the case when is large.With 1 Figure     

Ohm resistivity of electroless copper layers as a function of their thicknesses

The electric Ohm resistivity of electroless Cu depositions on dielectric substrates as a function of their thicknesses is studied. Substantial deviations (up to 10–20 times) from the standard resistivity ( = 1.7 cm^–1) below 0.5 (m thicknesses are observed. The experimental data show for the entire region of thicknesses (d 0.07–5 m) a power function between the relative resistivity changes (/) and the inverse thickness of depositions (d )–(/ (1/d )^0.8. This empirical relation is discussed as an effect of the porous structure of the metallic layers deposited on the substrate. A scanning electron micrography was applied in order to visualize the morphology of the depositions. The micrographs clearly show the evolution of the deposition profile: starting from separate islands at the very beginning of the process, and gradually covering the entire area with continuous but porous metal layers.     

Transport in the low-temperature limit of a Landau Fermi liquid

The Boltzmann equation for Landau quasiparticles is solved for T 0 by a specialization of a method discussed by Sykes and Brooker. The quasiparticle distribution function is expanded in Legendre polynomials, assuming a boundary condition which imposes axial symmetry, and even-order terms are assumed to relax together with relaxation time _e , odd-order terms with relaxation time _o . By letting wavelength , with finite, one obtains a first-sound solution, and by lettingT 0, and then , one obtains a zero-sound solution. When these solutions are used to calculate the pressure, it is found that the first-sound solution is consistent with hydrodynamics, exhibiting viscosity = _s , while the zero-sound velocityc ₁=[^–1(B₁+4/3_s)]^1/2, so that phenomenologically zero-sound propagates like a longitudinal elastic wave in a glass. A higher zero-sound mode is also predicted, but is heavily damped. The heat flux is calculated and found to obey Vernotte's equation, which contains an intertial term, added to Fourier's law, that becomes significant asT 0.     

Branching of the Falkner-Skan solutions for λ<0

Summary The Falkner-Skan equation f+ff+(1-f²)=0,f(0)=f(0), is discussed for <0. Two types of problems, one with f()=1 and another with f()=-1, are considered. For =0^- a close relation between these two types is found. For <-1 both types of problem allow multiple solutions which may be distinguished by an integer N denoting the number of zeros of f-1. The numerical results indicate that the solution branches with f()=1 and those with f()=-1 tend towards a common limit curve as N increases indefinitely. Finally a periodic solution, existing for <-1, is presented.     

Chebyshev polynomial approximation of the roots of the transcendental equation Μ tan Μ=b

A polynomial approximation of the roots of the equation tan=b are tabulated, valid uniformly on the interval b [0, ].Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 2, pp. 347–348, February, 1971.     

Boundary-layer similarity flows driven by a power-law shear over a permeable plane surface

Summary. The boundary-layer similarity flow driven over a semi-infinite permeable flat plate by a power-law shear with asymptotic velocity profile U(y)=y(y,>0) is considered in the presence of lateral suction or injection of the fluid (y denotes the coordinate normal to the plate). The analytically tractable cases =–2/3 and =–1/2 are examined in detail. It is shown that while for =–2/3 the adjustment of the flow over an impermeable plate to the power-law shear is not possible, in the permeable cases the presence of suction allows for a family of boundary-layer solutions with the proper algebraic decay. The value of the skin friction corresponding to this family of solutions is given by the parameter s=9³/(4f_w), where f_w denotes the suction parameter. In the limiting case of a vanishing suction and a properly vanishing value of the parameter (such that s=finite), this family of algebraically decaying solutions goes over into the (exponentially decaying) Glauert-jet. In the case =–1/2, solutions showing the proper algebraic decay were found both for suction ( f_w > 0) and injection ( f_w<0) in the whole range –<f_w<+. In this case the skin friction parameters s=2²/3 is independent of the suction/injection parameter f_w.     

The Problem of Relaminarization of Supersonic Turbulent Boundary Layers on Axisymmetric Bodies under Flight Conditions in the Presence of Heat Transfer

Analysis is made of the results of investigation of the problem of relaminarization of turbulent boundary layers under conditions of different kinds of stimulation of the field of flow. Results are given of flight aerophysical experiments involving the effect of relaminarization in a supersonic turbulent boundary layer for Re _L 10⁸, M4.5, and an acceleration a32g under conditions of aerodynamic heating. Quantitative data are given on the gradient criteria of stability of two types at starting points of relaminarization under flight conditions.     

On the proximity effect in a superconductive slab bordered by metal

The first Ginzburg-Landau equation for the order parameter in the absence of magnetic fields is solved analytically for a superconducting slab of thickness 2d bordered by semi-infinite regions of normal metal at each face. The real-valued normalized wave function f=/ depends only on the transversal spatial coordinate x, normalized with respect to the coherence length of the superconductor, provided the de Gennes boundary condition df/dx=f/b is used. The closed-form solution expresses x as an elliptic integral of f, depending on the normalized parameters d and b. It is predicted theoretically that, for b< and dd_c=arctan(1/b), the proximity effect is so strong that the superconductivity is completely suppressed. In fact, in this case, the first Ginzburg-Landau equation possesses only the trivial solution f0.     

A numerical method for flexible airfoils in incompressible inviscid flow

Summary The paper deals with the aerodynamic analysis of flexible airfoils, based on a quasi-lattice vortex method (QVLM). The analysis is formulated in matrix form and leads, as in other similar studies, to a linear algebraic system when the angle of attack is nonzero, and to an eigenvalue problem when the incidence angle is zero. The aerodynamic characteristic curvesC _L -,C _m - are presented. Finally, the airfoil shapes for several values of the tension coefficient and angles of attack are drawn. The results obtained with the present method are in good agreement with those reported in previous studies and evidentiate the flexibility of the QVLM as applied to flexible airfoils.Notation A aerodynamic matrix, defined in QVL method, (8) - B matrix, see Eq. (18) - c chord of airfoil - C matrix defined asAB - C _L lift coefficient, 2L/V ² c) - C _p moment coefficient, 2M/(V ² c ²) - C _p pressure coefficient,C _p =2p/(V ² ) - C _T tension coefficient, 2T/(V ² c) - D matrix, see Eq. (11) - I unit matrix - l curvilinear length of the flexible airfoil - N number of collocation points on the airfoil shape - q dynamic pressure, V ² /2 - T tension force in the sail - V freestream velocity - w downwash - x nondimensional coordinate,x/c - X _i control points, Eq. (9) - X _max dimensionless position of the maximum camber - Y _k source points, Eq. (9) - z coordinate normal tox axis - Z nondimensional coordinate,z/c - Z _s camber equation in dimensionless form,z _s /c - incidence with respect to the upstream flow velocity - column vector of the local curvatures {₁, ₂,..., _N } ^T - nondimensional membrane excess ratio - eigenvalue of the problem (23) - _k zeroes of the Chebyshev polynomia of the first kind, 1kN - column vector of the local slopes, {₀, ₁, ₂,..., _N } ^T - column vector, {₁, ₂,..., _N } ^T - ₀ slope at airfoil leading edge     

Functional derivative ofT c with α2(ω)F(ω) for weak coupling anisotropic superconductors

Approximate analytic calculations of the functional derivative ofT _c with respect to ²()F() for anisotropic superconductors are presented, with the primary purpose of identifying the determining material parameters. The square-well model for the phonon-mediated electron-electron interaction, the weak coupling limit ( _c /2T _c 1), and separable anisotropy are used. The general behavior of T _c /²()F() is the same as that found in numerical calculations for the case of small anisotropy, a ²/(–*)1; the regime of * is also discussed.     

Chebyshev approximation for the roots of the equation BiWГ(μ)=μVГ(μ)

A minimax approximation, uniform for Bi [0, ), is developed for the roots of the equation BiW()=V(), by means of Chebyshev polynomials.Translated from Inzhenero-Fizicheskii Zhurnal, Vol. 28, No. 4, pp. 710–715, April, 1975.     

Nonlinear asymptotic theory of hypersonic flow past a circular cone

Summary The hypersonic small-disturbance theory is reexamined in this study. A systematic and rigorous approach is proposed to obtain the nonlinear asymptotic equation from the Taylor-Maccoll equation for hypersonic flow past a circular cone. Using this approach, consideration is made of a general asymptotic expansion of the unified supersonic-hypersonic similarity parameter together with the stretched coordinate. Moreover, the successive approximate solutions of the nonlinear hypersonic smalldisturbance equation are solved by iteration. Both of these approximations provide a closed-form solution, which is suitable for the analysis of various related flow problems. Besides the velocity components, the shock location and other thermodynamic properties are presented. Comparisons are also made of the zeroth-order with first-order approximations for shock location and pressure coefficient on the cone surface, respectively. The latter (including the nonlinear effects) demonstrates better correlation with exact solution than the zeroth-order approximation. This approach offers further insight into the fundamental features of hypersonic small-disturbance theory.Notation a speed of sound - H unified supersonic-hypersonic similarity parameter, - K hypersonic similarity parameter, M - M freestream Mach number - P pressure - T temperature - S entropy - u, v radial, polar velocities - V freestream velocity - shock angle - cone angle - density - density ratio, /() - ratio of specific heats - polar angle - stretched polar angle, / - (), (), () gage functions     

Enhancement of heat transfer of mixed convection for heated blocks using vortex shedding generated by an oblique plate in a horizontal channel

Summary The problem of heat transfer enhancement of mixed convective flow past heated blocks in a horizontal channel is investigated. The heat transfer enhancement in this paper has been accomplished by the installation of an oblique plate to generate vortex shedding, which is used in flow modulation. Results for the details of the streamlines in the channel and the Nusselt number along the blocks with and without an oblique plate have been presented.Notation C _p pressure coefficient (2f Pds/f ds) - d length of an oblique plate - ds surface area increment along an oblique plate - f_s frequency of the vortex shedding - Gr Grashof number - H channel wall-to-wall spacing - h height of the block - k thermal conductivity - L channel length - Nu Nusselt number - time-mean Nusselt number (f Nudt/f dt) - average time-mean Nusselt number - n normal vector - P dimensionless pressure (p ^*/(u ² ) - p ^* pressure - Pr Prandtl number (/) - q heat flux at the block boundary - Re Reynolds number (u w/v) - St Strouhal number (df_ssin /u ) - T^* temperature - T uniform inlet temperature - t dimensionless time (t ^* / (w/u )) - t dimensionless time increment - t ^* time - u uniform inlet velocity - u, v dimensionless velocity components (u=u ^*/u ,v=v ^*/v ) - u ^*,v ^* velocity components - w width of the block - x,y dimensionlessx ^*,y ^* coordinates (x=x ^*/w,y=y ^*/w) - x ^*,y ^* physical coordinates - thermal diffusivity - angle of inclination for a plate - dimensionless temperature ((T^*–T ^* )/(qw/k)) - v kinematic viscosity of fluid     

Shear viscosity of liquid4He and3He-4He mixtures,especially near the superfluid transition

High-resolution measurements of are reported for liquid⁴He and³He-⁴He mixtures at saturated vapor pressures between 1.2 and 4.2 K with particular emphasis on the superfluid transition. Here is the mass density, the shear viscosity, and in the superfluid phase both and are the contributions from the normal component of the fluid ( _n and _n ). The experiments were performed with a torsional oscillator operating at 151 Hz. The mole fraction X of³He in the mixtures ranged from 0.03 to 0.65. New data for the total density and data for _n by various authors led to the calculation of . For⁴He, the results for are compared with published ones, both in the normal and superfluid phases, and also with predictions in the normal phase both over a broad range and close to T. The behavior of and of in mixtures if presented. The sloped/dT near T and its change at the superfluid transition are found to decrease with increasing³He concentration. Measurements at one temperature of versus pressure indicate a decreasing dependence of on molar volume asX(³He) increases. Comparison of at T, the minimum of _n in the superfluid phase and the temperature of this minimum is made with previous measurements. Thermal conductivity measurements in the mixtures, carried out simultaneously with those of , revealed no difference in the recorded superfluid transition, contrary to earlier work. In the appendices, we present data from new measurements of the total density for the same mixtures used in viscosity experiments. Furthermore, we discuss the data for _n determined for⁴He and for³He-⁴He mixtures, and which are used in the analysis of the data.     

Effect of Gamma Irradiation on the Piezoelectric Properties of K2Sr4Nb10O30–K6Li4Nb10O30 Solid Solutions

The effect of gamma irradiation on the dielectric ( ₃₃/₀, tan) and piezoelectric (d ₃₁, g ₃₁, K _p, Q _m) properties of ₂Sr₄Nb₁₀O₃₀–K₆Li₄Nb₁₀O₃₀ solid solutions (tetragonal tungsten bronze structure) was studied as a function of K₆Li₄Nb₁₀O₃₀ content. The results demonstrate that increasing the gamma dose to 9 × 10⁵ Gy reduces ₃₃/₀ and tan. With increasing Li⁺ content (filling of triangular channels), d ₃₁, g ₃₁, K _p, and Q _m increase. The results are interpreted in terms of the generation of stable defects and effective redistribution of the energy of gamma radiation over the ceramic sample.     

Formulas for evaluating the stabilization time of sluggish measuring instruments

Conclusions In this article formulas are suggested for calculating the stabilization time in ranges of 0<1 and 1.04<. These formulas are universal, they have a higher precision than has been hitherto obtained and they reflect the actual nature of the relationship between t_s and .Translated from Izmeritel'naya Tekhnika, No. 11, pp. 58–60, November, 1966.     

Dielectric properties of chemically treated wood

Dielectric properties along the grain for absolutely dried untreated and seven kinds of chemically treated Sitka spruce (Picea sitchensis Carr.) woods were measured. Cole-Cole's circular arc law was applied to the results of the relaxation due to the motions of methylol groups. The following changes were caused by chemical treatments. In polyethylene glycol (PEG) impregnation, the distribution of relaxation times became very narrow, the generalized relaxation time (_m) was considerably decreased, and the relaxation magnitude (₀ – ) was slightly increased. In acetylation, the distribution of relaxation times became very broad, _m was considerably increased, and (₀ – ) was remarkably decreased. In propylene oxide treatment, the distribution of relaxation times became slightly narrow and _m was decreased. _m was slightly decreased in formalization, phenol-formaldehyde (PF) resin treatment and wood methyl methacrylate (MMA) composite. (₀ – ) was decreased in formalization and PF-resin treatment and was hardly changed in wood-MMA composite and heat treatment. The distribution of relaxation times was almost unchanged in formalization, PF-resin treatment, wood-MMA composite and heat treatment.